Ionic pump



P 26, 1967 R. M. PHILLIHPS ETAL 3,343,781

IONIC PUMP Filed April 28, 1965 3 Sheets-Sheet l Y HIGH VOLTAGE 3 INVENTORSI ROBERTM. PHILLIPS,

GERARD C. VAN HOVEN,

THEI ATTORNEY.

Sept. 26, 1967 Filed April 28, 1965 R. M. PHILLIPS ETAL IONIC PUMP s Sheets-Sheet 2/ CURRENT Ma FIGA.

EMISSION GURRE NT C E N TE R CONDUCTOR CURRENT I J I I I 2 4 6 8 IO CURRENT AMPS IN 200 TURN COIL INVENTORSI 7 ROBERT M. PHILLIPS GERARD C. VAN HOVEN,

BY W

I; TH IR ATTORNEY.

Sept. 25, 1967 I R. M. PHILLIPS ETAL 3,343,781

IONIC PUMP 3 She ets-Sheet 5 Filed April 28, 1965 INVENTORS: ROBERT M. PHILLIPS, BY;

N E v WM ZM W 7 A hwflbn 0 R A T R United States Patent 3,343,781 IONIC PUMP Robert M. Phillips, Redwood City, and Gerard C. Van Hoven, Palo Alto, Calif., assignors to General Electric Company, a corporation of New York Filed Apr. 28, 1965, Ser. No. 451,384 16 Claims. (Cl. 230-69) ABSTRACT OF THE DISCLOSURE An ion pump with reduced magnetic fields wherein a spinning electron beam is utilized to generate ions which are gettered or otherwise removed from the system.

This invention relates to an ionic pump and more particularly to a spinning beam kind of ionic pump wherein a spinning electron beam is utilized to generate ions which are gettered or otherwise removed from the system.

Getter ion pumps are well known in the prior art and are adequately described for example in US. Patents 2,755,014, Westendorp et al. and 3,080,104, Vanderslice, each of which is assigned to the same assignee as the pres ent invention. In one form, a getter ion pump may be described as an envelope or enclosure having spaced apart coaxial cathode elements therein and an intermediate electron transparent anode. The anode and cathode assembly is subjected to or submerged in a magnetic field having lines of force directed substantially perpendicular to and through the anode. In this type of pump a glow discharge is established between the anode and cathodes so that gas molecules in the enclosed volume are ionized with the resultant positive ions striking the cathode surfaces to be trapped or embedded therein. Also, where the cathode is of a suitable metal and required potentials are available, sputtering takes place and the sputtered metal is condensed on or collects on the anode and other exposed surfaces of the pump. Gas cleanup therefore occurs in the described pump through gettering action of the deposits of metal on the anode and other surfaces and also by being entrapped or embedded in these surfaces.

A particular problem associated with these getter ion pumps relates to the necessity of having very large, cumbersome, and heavy magnetic structures in order to provide the required magnetic field. The necessary large size and weight of these magnets interfere with ordinary transporting, assembly, and disassembly procedures as well as exceeding in many instances the space available for the pump. Furthermore, the use of high strength magnetic fields limits the use of the getter ion pump to those applications where the magnetic field will not interfere with operations of other adjacent electron apparatus.

Prior getter ion pumps as mentioned are also somewhat restrictive in the length of the electron trajectories which may be established. However, a greater length increases the likelihood of an electron collision with a gas molecule to generate ions.

Accordingly, it is an object of this invention to provide an improved spinning electron beam getter ion pump.

It is a further object of this invention to provide a getter ion pump requiring only very small magnets and magnetic field.

It is another object of this invention to provide a small magnet getter ion pump of high capacity.

It is an object of this invention to provide an ionic pump wherein the capacity and speed of the pump are not dependent on magnet size.

It is yet another object of this invention to provide an axially extended geometrically cylindrical getter ion pump.

3,343,781 Patented Sept. 26, 1967 It is another object of this invention to provide a spinning beam ionic pump having a spinning hollow cylindrical beam of axially moving electrons which are reflected between two end plates.

It is another object of this invention to provide a purely electrostatic spinning electron beam getter ion pump.

It is yet another object of this invention to provide an improved spinning hollow cylindrical beam getter ion pump.

Briefly described, this invention is one of its preferred forms includes spaced apart outer and inner axially extending cylinders defining an annular closed ended pumping space therebetween. The outer cylinder is at cathode or negative potential while the inner cylinder is at anode or positive potential. An electron emitter means is provided at one end of the closed annular space to generate and direct a spinning cylindrical beam of electrons between and concentric with the described cylinders and moving from one end toward the other. The spinning electron beam produces ionization of a gas between the cylinders, and the resulting ions are propelled toward the outer or cathode cylinder to become embedded in the material thereof or to sputter the material. As the spinning ion beam approaches the opposite end of the cylinders, the beam is reflected for a reverse flow in the axial direction for further ionization purposes.

The novel features believed to be characteristic of the present invention are set forth in the appended claims. The invention itself, however, together with the further objects and advantages thereof, may be best understood with reference to the following description taken in connection with the drawings in which FIG. 1 is a cross-sectional view of one preferred embodiment of this invention;

FIG. 2 is an illustration of a magnet assembly which may be employed in FIG. 1;

FIG. 3 is an illustration of a thermionic emission element for the pump of this invention;

FIG. 4 is a series of curves representing current in the center conductor of FIG. 1 and the corresponding emission current;

FIG. 5 is a schematic illustration of magnetic circuit modifications of this invention;

FIG. 6 is a further schematic illustration of a magnetic circuit modification of this invention;

FIG. 7 is a schematic representation of a purely elec: trostatic embodiment of this invention.

Referring now to FIG. 1, there is illustrated a schematic cross section of one preferred embodiment of the spinning ion beam pump of this invention. In FIG. 1 getter ion pump 10 basically includes a pair of concentric cylinders 11 and 12 which together define an annular chamber 13. Cylinder 11 which is adapted to be connected to a suitable source of electric power as an anode may be in rod or hollow cylinder form and include various metals including those metals found particularly effective for gettering gases, i.e., titanium, tungsten, zirconium, et cetera. Cylinder 12 is adapted to be connected to a suitable source of electric power as a cathode. Cylinder 12 is of a getter metal or includes a getter metal, as described for cylinder 11, inner surface exposed to the anode cylinder 11.

Chamber 13 is closed at one end of pump 10 by an end plate 14 suitably vacuum sealed to the end of outer cylinder 12. At the other end of cylinder 12 there is provided a structural arrangement 15 which not only closes the end of the annular chamber 13 but also provides for the maintenance of anode 11 and cathode 12 in their illustrated relationship, and also electrically insulated from each other. More particularly, annular end plate 16 is concentrically positioned about anode cylinder 11 and is sealed at its outer periphery to the end of cathode cylinder 12. The inner lipped periphery 17 of end plate is joined by a suitable vacuum tight ceramicto-metal seal to one end of an electrically insulating hollow ceramic cylinder 18 which is also concentrically positioned about anode cylinder 11. The other end of the ceramic cylinder 18 is then joined to electrode 11 by means of a vacuum tight ceramic-to-metal seal between lip 19 of electrode 11 and cylinder 18. This arrangement provides for the support of cylindrical electrode 11 in cylinder 12 and with one face end 20 spaced from end plate 14. The other end is supported by the described ceramic-to-metal seals at lips 17 and 19. The flanged conduit 21 is provided to attach the pump 10 in gas or fluid flow relationship with a chamber to be evacuated. Thus the described structure is one including a defined annular chamber 13 which is vacuum tight other than through conduit connection 21.

By being connected to an enclosure to be evacuated, the annular chamber 13 contains a gas which is to be removed or otherwise trapped to reduce the pressure not only in the pump but also in the enclosure to be evacuated. This removaland entrapment takes place by means of ionization of the gas molecules through the use of a hollow spinning electron beam. In order to provide a spinning electron beam, in one form of this invention an electron source such as thermionically emissive element or filament 22 is employed. Filament 22 is illustrated in FIG. 1 as projecting through base wall 14 and includes a ring-shaped portion 23 having the periphery thereof generally within and concentric to the annular chamber 13. The legs 24 of emitter 22 then project through base plate 14 in a vacuum tight ceramic-to-metal sealed relationship for connection to a suitable source of power 25 externally of the pump. As illustrated in FIG. 1, for each leg 24, a well known type of ceramic-to-metal seal electrical lead through includes a first flared ferrule 26 sealed in vacuum tight relationship with the edge of an aperture 27 in base plate 14. An electrically insulating ceramic cylinder 28 is positioned concentrically with ferrule 26 and vacuum tight sealed thereto at one end. The other end of the cylinder 28 is sealed in vacuum tight relationship to a further ferrule 29. The arrangement described provides a vacuum tight ceramic-to-metal seal between legs 24 and base plate 14.

Suitable energization of the electron emitter means 22 from a source of power schematically illustrated as 25 provides a supply of electrons within annular chamber 13. The electrons provided are suitably controlled to form a hollow cylindrical beam which is concentric with the anode 11 and spaced between cylinders 11 and 12. The spinning electron beam travels or moves axially along the pump from the base plate 14 toward the end plate 15.

Various design parameters may be employed in order to generate and control such a cylindrical or tubular electron beam. For example, the teachings as disclosed in U.S. Patent 2,975,324, Cook, assigned to the same assignee as the present invention, may be so employed. In one form of this invention as illustrated in FIG. 1, the base plate 14 which is about 4 /2 inches diameter, includes a pair of ridges 30 and 31 defining spaces in which solenoid coils 32 and 33 are disposed. These solenoid coils include a first main coil 32, and a second control coil 33 which is utilized to control the magnetic field generated by the main coil 32. By operating the second coil 33 in opposing relationship to the main coil 32, an electromagnetic field is obtained which is almost or substantially radially directed, from an axial line, along the pump, which is positioned intermediate poles A and B as represented by the ridges 30 and 31 on end plate 14. When the power input to the electron emitter 22 is raised sufiiciently to cause thermionic emission, an electron will travel along the mentioned line and will see little if any component of the axial magnetic field.

An electrical field is established in the getter ion pump 10 by connecting anode and cathode cylinders 11 and 12 respectively to a source of power 34 sufficient to establish a requisite potential therebetween. Such a potent al of between 2000 and 5000 volts operates satisfactorily in this invention. As the electrons are emitted from filament 22 they are drawn toward the anode conductor 11 by the mentioned electric field. In this process they are given an angular velocity by the radial magnetic field and the resulting centrifugal force prevents the electrons from reaching the anode conductor 11. When the spinning beam of electrons reaches the free end 20 of anode 11 they will have passed beyond the influence of the magnetic field and Will be drifting toward end plate 15 with most of their energy, howover, directed in angular velocity. The centrifugal force will be balanced by the radial-electrical field force and the electrons will follow the path of a tight helix until they reach the end plate 15.

When an electron from this spinning beam strikes a gas molecule in the annular space 13 gas ions are generated. These ions carry a positive charge and are accelerated radially outwardly to the inner surface of outer cylinder 12. In order to trap or adsorb these gas ions, the inner surface of cylinder 12 is lined or covered or coated with a gas adsorbing or getter metal 35, with titanium being preferred. Alternately cylinder 12 could be wholly of titanium. or titanium alloys. When a positive ion is projected into the titanium surface it either is buried in the surface or otherwise entrapped in the surface, or causes sputtering of fresh titanium. This sputtered titanium may then be caught on exposed internal surfaces of the pump where it becomes active as a fresh titanium surface to absorb or getter more gas ions. Alternatively, a suitable structure may be provided within the pump to act as a sputtered metal receiving surface to additionally entrap larger numbers of gas ions. 1

It is essential to the most effective operation of this pump that the spinning electron beam be in the form of electrons most of which orbit the center electrode 11 in equidistant relationship or concentric relationship therewith so as to provide axial travel over a substantial length of the pump. A longer axial travel, compatible with the design parameters necessary to provide a spinning electron beam, increases the efficiency of the pump. As a practical matter it has been found that the pump should have an axial dimension for the spinning beam which is greater than the diameter of the outer cylinder.

The effectiveness of this pump in providing a great num ber of positive ions is increased where those electrons which have spiraled about the center electrode 11 and reached end plate 15 are reflected to again spiral about central electrode 11 toward end plate 14. This reflectivity may take place by means of a force field including magnetic, electric, or electrostatic means, or combinations thereof. In order to provide magnetic reflectivity a small magnetic coil 36 surrounds the center electrode support. In addition, a steel sleeve 37 may be inserted into anode 11, which is in the form of a hollow cylinder, for a distance of several inches beyond the reflection end of the pump. Sleeve 37 is employed to minimize the axial magnetic field for a given amplitude of radial field in the reflecting region. An electron from the spinning electron beam which has traversed the axial distance of the pump without collision with a gas molecule to provide a positive ion will continue to follow the path of a tight helix until it reaches the radial magneto field caused by the solenoid 36 at end plate 15. At this point the electron crosse more flux from the magnet which converts the remaining axial energy into rotation, causing the electron to be turned back. After the electron leaves the magnetic mirror region the angular velocity will be substantially the same as the approach to the magnetic mirror, but the axial velocity will have reversed direction. Upon reaching the original magnetic field the electron will unspin itself just reaching the filament with a velocity diminishing to zero and will then turn and start the traversal once more. In the ideal situation it is only necessary to supply enough electrons from the filament to replace those lost during the ionization collision process.

In place of the solenoid coils as described, both for the base end and reflecting end of the pump, permanent magnets may also be employed to provide the same functional purposes. For example, referring now to FIG. 2, there is illustrated an arrangement of magnets which performed effectively in the operation of the pump of FIG. 1. In FIG. 2 the end plate 14 of the pump is of stainless steel and has attached thereto a pair of steel rings 38 and 39 concentric with each other. These rings are also concentric with the pump assembly in that the outer ring 38 is generally concentric with the annular chamber 13 while the inner ring 39 is concentrically spaced with the end of the inner cylinder 11. In one instance nine horseshoe type permanent magnets 40 were employed each of which bridged the gap between the rings 38 and 39 as illustrated. Ttests were made using the permanent magnet structure as illustrated as substitution for the ZOO-turn solenoid coils as previously described. Data on emission and anode current as a function of pump voltage indicated that the permanent magnet structure was equivalent to 1350 ampere turns in the large diameter coil and 1600 ampere turns in the small diameter coil. The radius of the structure was chosen as the average of the coil circuits. The magnet structure weighed about 1% pounds as compared to a comparable getter ion type pump as mentioned in the prior art requiring about 16 pounds of magnet structure. The same magnet structure may be used for the reflecting end of the pump.

FIG. 3 illustrates a modification of the electron emitter which may be employed in this invention. Referring now to FIG. 3, the emitter assembly 41 includes a pair of frames 42 and 43 formed of stainless steel strips to define half-moon sectors of a circle. The transverse members 44 and 45 which define the half-moon sectors are in spaced apart relationship so that in general a complete circle is defined with the exception of the peripheral space between the mentioned transverse members. Bridging the space between the mentioned transverse members are a pair of thoriated iridium filaments 46 and 47. To complete the assembly, a pair of pin connectors 48 and 49 are attached to the transverse members perpendicularly there to to project outside of the pump, as described with respect to the filament 22, to support the thoriated iridium filament and the half-moon sectors transversely within the housing 11.

In an operative embodiment of the spinning beam pump as described, utilizing permanent magnet structure and a thoriated iridium filament, the ion pump was connected to a chamber wherein the pressure was about 10 mm. of mercury and the ion pump pumped this chamber through a pressure of IX l mm. of mercury. Pumping was done at about 1000 volts potential with the filament sections operating in parallel at 8 amps and about 15 watts filament power. The parameters recorded were emission current and center conductor current as a function of pump voltage, amplitude and shape of the magnetic field at the filament, and amplitude of the field at the beam reflection end of the pump. FIG. 4 illustrates typical curves of emission current and anode conductor current taken with no field at the reflection end of the pump and a single coil at the filament end. The pump voltage was maintained at 1000 volts while the filament coil current was varied. The anode conductor current is only a small fraction of the emission current with a large magnetic field, indicating that most of the current which leaves the interaction region reaches the grounded side of the pump. The current arrives with nearly zero volt velocity and hence requires no power. It was observed that under some conditions ionic pumping was obtained with a cold filament and no emission current. The pumping was especially apparent at relatively high system pressures of about x mm.

of mercury and above, and with a relatively large magnetic field amplitude. Pumping in the absence of filament supplied electrons should be expected when more of the electrons formed in the ionizing process occupy stable orbits than are lost in ionizing collisions or collisions with the walls. Under this condition a single electron would be capable of starting a sustained interaction.

In order to increase the surface area available for sputtered titanium, a suitable surface increasing member such as a honeycomb type sheet metal structure may be utilized which surrounds the center electrode. Such an assembly may be in the form of a columnar multicellular or grid-like member surrounding the central cylindrical electrode and operative to collect sputtered titanium from the wall surface 35. Such a multicellular or increased surface area member may also be placed adjacent to and along the inside surface of the outer cylinder to be receptive to sputtered titanium from that surface and, by the same token, this member could also be a part of the inside wall. A partial section of an exemplary multicellular wall is illustrated in FIG. 1 at 50. Wall 50 may be of the same potential as the cylinder 12, or may be insulated therefrom and have a suitable control potential applied thereto which will be advantageous for ion control as well as for a getter material condensing or coating surface. Multicellular or ion transparent wall 50 may take various configurations and extend to cover or shield predetermined areas of cylinder 12 or most of it. A preferable configuration is a cylinder structure 50 extending transversely along most of the inner surface 35 of cylinder 12. Wall or cylinder structure 50 as a separate electrode provides the pump of this invention with the characteristics of known triode ionic pumps.

The weight of the magnets 40 may also be reduced by changing the shape of the pump in the region of the magnetic field, i.e., at the end plates. These end plates could be in the shape of a truncated cone to bring the magnet structure over the filament.

Referring now to FIGS. 5 and 6, there is shown a schematic illustration of a modification of this invention wherein a double-ended pump is employed. In the pump 51 of FIG. 5 it is noted that the radial components of the magnetic field are aiding electron beam spinning, and in the pump 52 of FIG. 6, the radial components are opposing electron beam spinning. In the former instance electrons from one filament would be reflected by the magnetic field at the other end of the pump. In the latter instance electrons from one filament would be indistinguishable from those originating at the other, in the sense that each electron is completely unspun and just reaches the filament at each end of the pump. In the former case, electrons from the two filaments spin in opposite directions; in the latter all electrons spin in the same direction. Secondary emission could also be utilized to provide newly formed electrons in a filamentless pumping arrangement.

Operation of a vacuum pump in accordance with the teachings of this invention and utilizing a pump structure as illustrated in FIG. 1 led to the discovery that such a pump as previously described may be suitably modified to provide efiective gas pumping without a magnetic field. In the first instance it was discovered that proper proportioning of the pump obviates the magnetic field at the reflection end of the pump since beam reflection at that end may be produced by an axial component of the electric field as known in the art. Carried further, it was discovered that a purely electrostatic spinning beam ion pump operates effectively as a vacuum pump. Such a pump is illustrated in FIG. 7. Referring now to FIG. 7, there is schematically illustrated a pump 53 which takes the general constructional features of the pump of FIG. 1. More particularly, in FIG. 7 the inner cylindrical electrode 54 is attached to but electrically insulated from both ends 56 and 57 of the pump, to provide a coextensive annular chamber 58 from one end of the pump to the other. A suitable electron emitting gun 59 is positioned intermediate the ends of the pump along the side wall and is so positioned and arranged to direct electrons into a prescribed orbit around the center electrode. This balanced orbit, as depending upon the electric field plus the directing of the electrons, includes an axial component of velocity which provides electron travel axially along the inner electrode. Upon reaching one end of the pump these electrons are reversed through the action of the electrical field and proceed along the center electrode to the other end of the pump. These orbiting electrons are involved in collisions with the gas molecules in the annular space and generate ions as described with respect to the pump of FIG. 1.

Pump 53 incorporates a simple electron gun which is so oriented that it introduces both axial and angular components of velocity to the electrons emitted. The angular component obviates the need for a magnetic field to impart the initial spin to the beam. As in the original spinning beam pump of FIG. 1, the electrons from the gun progress coaxially down the structure, spinning around the center electrode, and are balanced between inward radial electric force and outward centrifugal force. At the end of the pump they are reflected by the mentioned axial component of electric field and spin back around the center conductor past the gun to the opposite end of the pump where they are again reflected. The geometry for such a pump has the advantage over preceding spinning beam ion pumps as previously described by eliminating all magnetic fields. The beam current may be maintained in the electron cloud as based upon the amount of charge density which can in turn be maintained by the spinning beam flow principle rather than by the smaller gun perveance established by the magnetic field in the earlier pump.

The objects of this invention have thus been obtained by the use of a spinning beam ion pump where the spinning beam is in the form of a cylinder whose axial dimension is substantially longer than the transverse dimension. The low axial component velocity and the rapidly spinning ion beam provide a very great electron path or orbit during which a collision of an electron with a gas molecule is likely. It is because of the extensive axial direction with a low component of axial velocity which acts to provide an effective ion pumping unit. Such a pump may be utilized as a complete pump or in combination with other types of pumps. For example, a getter such as titanium may be vaporized within the pump of this invention to increase the pumping characteristics. The vaporization of a metal such as titanium may take place by means of a separate heater for heating titanium or by other means of heating titanium parts.

In all pump embodiments as described the trajectory of the electrons about the center electrode are preferably circular and preferably equidistant from the center electrode coextensively in an axial direction. However, combinations of trajectories including circular, cycloidal or conical may be utilized in combination with a predetermined axial component so that electrons eifectively sweep a substantial axial dimension, preferably repetitively. The electrons are originally directed both for the circular orbit and the axial travel with, of course, potential collisions with gas molecules interrupting their trajectories. Primarily the electrons do not strike the central electrode but spiral thereabout for ion generating collisions which is the optimum means for pumping since the ions are trapped or driven into the outer getter wall. Other pumping mechanisms are of a secondary nature.

While this invention has been described with reference to particular and exemplary embodiments thereof, it is to be understood that numerous changes can be made by those skilled in the art without actually departing from the invention as disclosed, and it is intended that the appended claims include all such equivalent variations as come within the true spirit and scope of the foregoing disclosure.

What is claimed and desired to be secured by Letters Patent of the United States is:

1. A spinning beam ion pump comprising in combination,

(a) an envelope structure adapted to be evacuated,

(b) said envelope having a gas getter metal on its inner surface,

(c) said envelope adapted to be connected to a source of power at one potential,

(d) a cylindrical electrode in said envelope and defining an annular interaction space therewith,

(e) said electrode adapted to be connected to a source of power at a different potential,

(f) electron emitting means in said envelope,

(g) means to control electrons in said interaction space to prevent substantial electron striking of said cylindrical electrode and to provide a circularly spinning electron beam concentric with said cylindrical electrode and progressing slowly axially therealong,

(h) said spinning beam causing electron-gas molecule collisions to provide positive gas ions which are accelerated into said gas gettering metal for entrapment and to reduce the pressure in said envelope, and

(i) an ion transparent electrode positioned transversely between said envelope and said cylindrical electrode.

2. The invention as recited in claim 1 wherein said ion transparent electrode is adapted to have a potential applied thereto which is different from that of said envelope and said cylinder.

3. A spinning beam ion pump comprising in combination,

(a) a cylindrical envelope enclosure adapted to be connected to a source of power as a cathode,

(b) said cylindrical enclosure having its inner surface of a good gas gettering metal,

(c) a cylindrical electrode positioned concentrically in said enclosure to define an annular interaction space therein,

((1) said cylindrical electrode adapted to be connected to a source of power as an anode,

(e) thermionic electron emitting means in said enclosure adjacent one end thereof,

(f) force field means adjacent said enclosure,

(g) said force field means and said electron emitting means being constructed and positionally interrelated functionally to prevent substantial electron striking of said cylindrical electrode and to provide a hollow cylindrical spinning beam of electrons concentric with said cylindrical electrode and moving axially therealong from one end of said cylindrical electrode to the other,

(h) said spinning electron beam causing electron-gas molecule collisions in said interaction space to generate positive gas ions which are accelerated into said gas gettering metal for entrapment therein to reduce the gas pressure in said cylindrical enclosure.

4. The invention as recited in claim 2 wherein said force field means is electrical.

5. The invention as recited in claim 2 wherein said force field means is magnetic.

6. The invention as recited in claim 2 wherein said force field is electrostatic.

7. The invention as recited in claim 3 wherein increased area collecting surface means is interposed in said annular space to collect gas getter metal sputtered from said enclosure wall.

8. The invention as recited in claim 3 wherein said surface is a part of said enclosure wall.

9. The invention as recited in claim 3 wherein said collecting surface means is a separate structure.

10. The invention as recited in claim 3 wherein said collecting surface means is adjacent the wall of said cylindrical enclosure.

11. A spinning beam ion pump comprising in combination,

(a) a cylindrical enclosure adapted to be connected to a source of power as a cathode,

(b) said cylindrical enclosure having its inner surface of a good gas gettering metal,

(c) a cylindrical electrode positioned concentrically in said enclosure to define an annular interaction space therein,

(d) thermionic electron emitting means in said envelope adjacent one end thereof,

(e) force field means adjacent the said one end of said envelope having said emitting means,

(f) said force field means and said electron means being constructed and positionally interrelated functionally to prevent substantial electron striking of said cylindrical electrode and to provide a hollow cylindrical spinning beam of electrons concentric with said cylindrical electrode and moving axially therealong from one end of said cylindrical electrode to the other.

(g) further force field electron reflection means adjacent the opposite end of said electrode to reflect said axial progressing electrons in the reverse direction axially,

(h) said spinning electron beam causing electron-gas molecule collisions in said interaction space to generate positive gas ions which are accelerated into said gas gettering metal for entrapment therein to reduce the gas pressure in said cylindrical enclosure.

12. A spinning beam ion pump comprising in combination,

(a) a cylindrical enclosure adapted to be connected to a source of power as a cathode,

(b) said cylindrical enclosure having its inner surface of a good gas gettering metal,

(c) a cylindrical electrode positioned concentrically in said enclosure to define an annular interaction space therein,

(d) said cylindrical electrode adapted to be connected to a source of power as an anode,

(e) thermionic electron emitting means in said envelope adjacent one end thereof,

(f) magnetic field means adjacent the said one end of said envelope having said emitting means,

(g) said magnetic means and said electron means being constructed and positionally interrelated functionally to provide a hollow cylindrical spinning beam of electrons concentric with said cylindrical electrode and moving axially therealong from one end of said cylindrical electrode to the other,

(h) magnetic field electron reflection means adjacent the other end of said electrode to reflect said axial progressing electrons in the reverse direction axially,

(i) said spinning electron beam causing electron-gas molecule collisions in said interaction space to gener ate positive gas ions which are accelerated into said gas gettering metal for entrapment therein to reduce the gas pressure in said cylindrical enclosure.

13. The invention as recited in claim 12 wherein said magnetic field reflection means reflects and reverses said spinning beam axially and circumferentially.

14. A spinning beam ion pump comprising in combination,

(a) a cylindrical enclosure adapted to be connected to a source of power as a cathode,

(b) said cylindrical enclosure having its inner surface of a gas gettering reactive metal,

(0) a cylindrical electrode projecting into said cylindrical enclosure from one end thereof to define an axial space between the free end of said electrode and the other end of said cylindrical enclosure,

((1) said cylindrical electrode defining a further annular interaction space between the wall of said cylindrical enclosure and said projecting electrode,

(c) said cylindrical electrode adapted to be connected to a source of power as an anode,

(f) an annular thermionic emissive filament in said axial space and concentric with the free end of said cylindrical electrode and in surrounding relationship thereto,

(g) magnetic field means outside of said cylindrical enclosure and adjacent the end of said cylindrical enclosure adjacent said axial space,

(h) said magnetic field means and said electron means being constructed and positionally interrelated functionally to provide a hollow cylindrical spinning beam of electrons concentric with said cylindrical electrode and moving axially therealong from one end of said cylindrical electrode to the other,

(i) magnetic field electron reflection means at the other end of said electrode to reflect said axial progressing electrons in the reverse direction axially,

(j) said magnetic fields being operative to prevent substantial electron striking of said cylindrical electrode,

(k) said spinning electron beam causing electron-gas molecule collisions in said interaction space to generate positive gas ions which are accelerated into said gas gettering metal for entrapment therein to reduce the gas pressure in said cylindrical enclosure.

15. The invention as recited in claim 14 wherein said projecting electrode is hollow to contain an axially adjustable magnetic cylinder operative to effect and control said magnetic fields.

16. The invention as recited in claim 14 wherein means are included to heat and evaporate a getter metal in said interaction space.

References Cited OTHER REFERENCES Bulletin of American Physical Society, volume 8, No. 4, pages 336 and 337.

ROBERT M. WALKER, Primary Examiner.

Spring 1963, 

1. A SPINNING BEAM ION PUMP COMPRISING IN COMBINATION, (A) AN EVELOPE STRUCTURE ADAPTED TO BE EVACUATED, (B) SAID ENVELOPE HAVING A GAS GETTER METAL ON ITS INNER SURFACE, (C) SAID ENVELOPE ADAPTED TO BE CONNECTED TO A SOURCE OF POWER AT ONE POTENTIAL, (D) A CYLINDRICAL ELECTRODE IN SAID ENVELOPE AND DEFINING AN ANNULAR INTERACTION SPACE THEREWITH, (E) SAID ELECTRODE ADAPTED TO BE CONNECTED TO A SOURCE OF POWER AT A DIFFERENT POTENTIAL, (F) ELECTRON EMITTING MEANS IN SAID ENVELOPE, (G) MEANS TO CONTROL ELECTRONS IN SAID INTERACTION SPACE TO PREVENT SUBSTANTIAL ELECTRON STRIKING OF SAID CYLINDRICAL ELECTRODE AND TO PROVIDE A CIRCULARLY SPINNING ELECTRON BEAM CONCENTRIC WITH SAID CYLINDRICAL ELECTRODE AND PROGESSING SLOWLY AXIALLY THEREALONG, (H) SAID SPINNING BEAM CAUSING ELECTRON-GAS MOLECULE COLLISIONS TO PROVIDE POSITIVE GAS IONS WHICH ARE ACCELERATED INTO SAID GAS GETTERING METAL FOR ENTRAPMENT AND TO REDUCE THE PRESSURE IN SAID ENVELOPE, AND (I) AN ION TRANSPARENT ELECTRODE POSITIONED TRANSVERSELY BETWEEN SAID ENVELOPE AND SAID CYLINDRICAL ELECTRODE. 